Error request does not contain multipart / form-data or multipart / mixed stream

I'm trying to save the image to disk but it's giving me this error.

mai 18, 2015 12:03:56 PM com.sun.faces.lifecycle.ApplyRequestValuesPhase execute
ADVERTÊNCIA: javax.servlet.ServletException: org.apache.tomcat.util.http.fileupload.FileUploadBase$InvalidContentTypeException: the request doesn't contain a multipart/form-data or multipart/mixed stream, content type header is application/x-www-form-urlencoded;charset=UTF-8
javax.faces.FacesException: javax.servlet.ServletException: org.apache.tomcat.util.http.fileupload.FileUploadBase$InvalidContentTypeException: the request doesn't contain a multipart/form-data or multipart/mixed stream, content type header is application/x-www-form-urlencoded;charset=UTF-8
    at org.primefaces.component.fileupload.NativeFileUploadDecoder.decode(NativeFileUploadDecoder.java:44)
    at org.primefaces.component.fileupload.FileUploadRenderer.decode(FileUploadRenderer.java:44)
    at javax.faces.component.UIComponentBase.decode(UIComponentBase.java:831)
    at javax.faces.component.UIInput.decode(UIInput.java:771)
    at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1226)
    at javax.faces.component.UIInput.processDecodes(UIInput.java:676)
    at org.primefaces.component.api.UIData.process(UIData.java:336)
    at org.primefaces.component.api.UIData.processChildren(UIData.java:323)
    at org.primefaces.component.api.UIData.processPhase(UIData.java:285)
    at org.primefaces.component.api.UIData.processDecodes(UIData.java:245)
    at javax.faces.component.UIForm.processDecodes(UIForm.java:225)
    at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1221)
    at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1221)
    at org.primefaces.component.layout.Layout.processDecodes(Layout.java:226)
    at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1221)
    at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1221)
    at javax.faces.component.UIViewRoot.processDecodes(UIViewRoot.java:929)
    at com.sun.faces.lifecycle.ApplyRequestValuesPhase.execute(ApplyRequestValuesPhase.java:78)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:516)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1086)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:659)
    at org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:223)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1558)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1515)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)
Caused by: javax.servlet.ServletException: org.apache.tomcat.util.http.fileupload.FileUploadBase$InvalidContentTypeException: the request doesn't contain a multipart/form-data or multipart/mixed stream, content type header is application/x-www-form-urlencoded;charset=UTF-8
    at org.apache.catalina.connector.Request.parseParts(Request.java:2789)
    at org.apache.catalina.connector.Request.getParts(Request.java:2636)
    at org.apache.catalina.connector.Request.getPart(Request.java:2813)
    at org.apache.catalina.connector.RequestFacade.getPart(RequestFacade.java:1089)
    at org.primefaces.component.fileupload.NativeFileUploadDecoder.decodeSimple(NativeFileUploadDecoder.java:50)
    at org.primefaces.component.fileupload.NativeFileUploadDecoder.decode(NativeFileUploadDecoder.java:34)
    ... 42 more
Caused by: org.apache.tomcat.util.http.fileupload.FileUploadBase$InvalidContentTypeException: the request doesn't contain a multipart/form-data or multipart/mixed stream, content type header is application/x-www-form-urlencoded;charset=UTF-8
    at org.apache.tomcat.util.http.fileupload.FileUploadBase$FileItemIteratorImpl.<init>(FileUploadBase.java:800)
    at org.apache.tomcat.util.http.fileupload.FileUploadBase.getItemIterator(FileUploadBase.java:256)
    at org.apache.tomcat.util.http.fileupload.FileUploadBase.parseRequest(FileUploadBase.java:280)
    at org.apache.catalina.connector.Request.parseParts(Request.java:2725)
    ... 47 more

Here's my bean class

package br.com.drogaria.bean;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.Serializable;

import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
import javax.faces.context.FacesContext;
import javax.servlet.ServletContext;

import org.primefaces.model.UploadedFile;

import br.com.drogaria.domain.Produto;
import br.com.drogaria.util.FacesUtil;
import br.com.drogaria.util.Redimensiona;

@ManagedBean
@SessionScoped
public class Fileupload implements Serializable{

    /**
     * 
     */
    private static final long serialVersionUID = 1L;
    private Produto produtoCadastro;
    private UploadedFile arquivo;


    public String gravarImagem() {

        try {

            FacesContext context = FacesContext.getCurrentInstance();

            // pega informa��es do contexto para
            // conseguir o caminho f�sico
            // necess�rio para fazer o upload de arquivo
            ServletContext sc = (ServletContext) context.getExternalContext()
                    .getContext();



            // verifica se h� um arquivo para salvar
            if (arquivo != null) {

                // o tipo de arquivo
                String tipoDeArquivo = arquivo.getContentType();            

                if (tipoDeArquivo.equals("image/jpeg")
                        || tipoDeArquivo.equals("image/pjpeg")
                        || tipoDeArquivo.equals("image/gif")) {

                    InputStream stream = arquivo.getInputstream();

                    int fSize = (int) arquivo.getSize();
                    byte[] buffer = new byte[(int) fSize];
                    String nomeArquivo = this.separaNomeImagem(arquivo
                            .getFileName());

                    // chama o m�todo que salva o arquivo
                    Boolean salvarImagem = this.salvarArquivo(buffer, stream,
                            nomeArquivo, fSize, sc.getRealPath("/imagens"));

                    if (!salvarImagem) {
                        FacesUtil.adicionarMsgErro("Problema no upload do arquivo");
                    }

                    // cria um thumb se a imagem foi salva
                    if (salvarImagem) {
                        // redimensiona a imagem
                        Boolean salvarThumb = Redimensiona.redimensionar(
                                nomeArquivo, sc.getRealPath("/imagens"), sc
                                        .getRealPath("/thumbs"), 100, 100, 70);

                        if (!salvarThumb) {
                            FacesUtil.adicionarMsgErro("Problema ao salvar o Thumb");
                        }

                    }// fim do thumb

                    produtoCadastro.setImagem(nomeArquivo);


                }// fim do if tipoDeArquivo
                else {
                    FacesUtil.adicionarMsgErro("aceito somente JPEG, PJPEG ou GIF.");
                }
            }


        } catch (IOException e) {
            FacesUtil.adicionarMsgErro("Um erro ocorreu");
            e.printStackTrace();
        }

        return "sucesso";

    }

    // salva o arquivo no disco
    public boolean salvarArquivo(byte[] buf, InputStream stream,
            String nomeArquivo, int size, String path)
            throws FileNotFoundException, IOException {

        nomeArquivo = this.separaNomeImagem(nomeArquivo);

        File file = new File(path + "/" + nomeArquivo);

        FileOutputStream output = new FileOutputStream(file);
        try {
            while (true) {
                int count = stream.read(buf, 0, size);
                if (count == -1)
                    break;
                output.write(buf, 0, count);

            }
        } catch (Exception ex) {
            ex.printStackTrace();
            return false;
        }

        finally {
            output.flush();
            output.close();
            stream.close();
        }
        return true;

    }

    // separa o caminho f�sico do nome do arquivo
    private String separaNomeImagem(String nomeImagem) {

        if (nomeImagem.lastIndexOf("\") >= -1) {
            nomeImagem = nomeImagem.substring(nomeImagem.lastIndexOf("\") + 1);
        } else if (nomeImagem.lastIndexOf("/") >= -1) {
            nomeImagem = nomeImagem.substring(nomeImagem.lastIndexOf("/") + 1);
        }

        return nomeImagem;
    }

    public Produto getProdutoCadastro() {
        return produtoCadastro;
    }

    public void setProdutoCadastro(Produto produtoCadastro) {
        this.produtoCadastro = produtoCadastro;
    }

    public UploadedFile getArquivo() {
        return arquivo;
    }

    public void setArquivo(UploadedFile arquivo) {
        this.arquivo = arquivo;
    }





}

Here is the page

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml"
    xmlns:ui="http://java.sun.com/jsf/facelets"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:p="http://primefaces.org/ui">

<ui:composition template="/templates/modeloGeral.xhtml">
    <ui:define name="metadata">
        <f:metadata>
            <f:event listener="#{produtoBean.carregarPesquisa}"
                type="preRenderView" />
        </f:metadata>
    </ui:define>

    <ui:define name="conteudo">
        <h:form>
            <p:toolbar>
                <f:facet name="left">
                    <h:outputText value="Produtos" />
                </f:facet>
            </p:toolbar>

            <p:dataTable emptyMessage="Nenhum registro encontrado."
                value="#{produtoBean.listaProdutos}"
                filteredValue="#{produtoBean.listaProdutosFiltrados}" var="produto"
                rows="5" paginator="true">

                <f:facet name="footer">
                    <p:button value="Novo" outcome="/pages/produtoCadastro.xhtml">
                        <f:param name="proacao" value="Novo" />
                    </p:button>
                </f:facet>

                <p:column headerText="Código">
                    <h:outputText value="#{produto.codigo}" />
                </p:column>

                <p:column headerText="Descrição" filterBy="#{produto.descricao}"
                    sortBy="#{produto.descricao}">
                    <h:outputText value="#{produto.descricao}" />
                </p:column>

                <p:column headerText="Preço" sortBy="#{produto.preco}">
                    <h:outputText value="#{produto.preco}">
                        <f:convertNumber type="currency" currencySymbol="R$" />
                    </h:outputText>
                </p:column>

                <p:column headerText="Quantidade">
                    <h:outputText value="#{produto.quantidade}" />
                </p:column>
                <p:column headerText="Opções">

                    <p:button value="Excluir" outcome="/pages/produtoCadastro.xhtml">
                        <f:param name="procod" value="#{produto.codigo}" />
                        <f:param name="proacao" value="Excluir" />
                    </p:button>

                    <p:button value="Editar" outcome="/pages/produtoCadastro.xhtml">
                        <f:param name="procod" value="#{produto.codigo}" />
                        <f:param name="proacao" value="Editar" />
                    </p:button>


                </p:column>
                <p:column>

                    <p:fileUpload value="#{fileupload.arquivo}" mode="simple"
                        update="growl" />
                    <p:commandButton value="Procurar" action="#{fileupload.produtoCadastro}">
                     <f:ajax execute="@all" render="@form"/>
                    </p:commandButton>  
                </p:column>

            </p:dataTable>
        </h:form>
    </ui:define>
</ui:composition>
</html>

here is my Web.xml file

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
    id="WebApp_ID" version="3.1">
    <display-name>Drogaria</display-name>
    <welcome-file-list>
        <welcome-file>pages/principal.xhtml</welcome-file>
    </welcome-file-list>
    <servlet>
        <servlet-name>Faces Servlet</servlet-name>
        <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>Faces Servlet</servlet-name>
        <url-pattern>*.xhtml</url-pattern>
    </servlet-mapping>
    <listener>
        <listener-class>br.com.drogaria.util.ContextListener</listener-class>
    </listener>




</web-app>

I wanted to know why you are giving the error message, and I would like to correct and solve the problem.